^+1 on the X6. This will benefit a lot esp. if using programs like 3DS or Maya and the program you use (GemVision) is multi-threaded.
For the motherboard, I personally keep away from MSI so I would recommend this: http://www.newegg.com/Product/Product.aspx?Item=N82E16813128438
GA-890XA-UD3 790X ~$105 after MIRhttp://www.newegg.com/Product/Product.aspx?Item=N82E16813131406
ASUS M4A785TD-M EVO AM3 $80
Get the ASUS if you plan to only run a single GPU (for rendering, a single GPU will do) and if you are on a tight budget. A GTS240/210,etc will work fine. If you don't mind modding, you can get a old 8800GTS and softmodd it in to a Quadro.
Note: I'm recommending the X6 assuming the software is properly multithreaded. If it is not, get a high clocked X4.